ROLE OF READSORPTION DURING CO HYDROGENATION OVER COBALT MODEL CATALYSTS

The role of readsorption of ethene during carbon monoxide hydrogenation has been studied on polycrystalline cobalt foils and on thin cobalt films evaporated onto a gold substrate, using a combination of UHV studies and atmospheric pressure reactions at 525 K and at 101 kPa total pressure. On the cobalt foils we have detected C1-C5 hydrocarbons and on the Co/Au surfaces C1-C4 hydrocarbons. On both surfaces the product distribution shifts towards higher molecular weight hydrocarbons when increasing amounts of ethene are added. The amounts of various hydrocarbons formed on the surface are explained in terms of a simplified reaction model where alpha-hydrogenation is the rate-limiting step. The results indicate that multiple readsorption is required to produce higher molecular weight hydrocarbons in industrial catalysts.